Exim email configuration for Dev server

Hi, I'm trying to configure the Exim mail transport program on my Dev server to send all outgoing emails to my local user account, regardless of user or domain. For example, if a user sends an email to bob@gmail.com or henry@hotmail.com, they should all be sent to my local user mailbox.

After consulting Google for a while, I was told to add the following to the exim config file:

catch_all_outgoing:
driver = redirect
data = my_user
unseen

While this does send all emails to my selected local user mailbox, it also sends an error message to the same user as well as to user "www-data", saying

"A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:

blablabla@bla.com
Mailing to remote domains not supported"

Does anyone know how to get rid of the error messages or of a better way to do this?

Thanks!